(a) Technical Field of the Invention
The present invention is related to a bidirectional digital communication circuit and a bidirectional digital communication method, which are suitable for network and interface technology applied to digital communication systems such as fiber communication, digital wireless system and video system, or the like for example, HDMI (High Definition Multimedia Interface) and DVI (Digital Visual Interface) applications.
(b) Description of the Prior Art
Digital communications are widely applied for audio, video and data transmission, and data types are getting more and more complex. More and more protocols are developed to communicate two or more devices. Modern products may include two or more different protocols to be compatible with other products or old devices. It makes the modern communication device become more and more complex, too.
For example, the video interfaces, such as DVI and HDMI, always have huge data flow for uncompressed signals and other control channels to achieve the video transmission. The multi-channels interface makes the high cost, especially some special products need to include other functions, such like IR (Infrared) remote control, RS-232 (EIA-RS-232). People always want to have a powerful product that includes all functions in a small package. Therefore, how to establish reliable communications with minimum channels that meet cost effective and performance is a challenge.
There are some related arts are disclosed, such as US patent publication No. 2008/0152024 A1 (titled “Two-way communication circuit, two-way communication system, and communication method of two-way communication circuit”), US patent publication No. 2008/0201756 A1 (titled “Multi-media digital interface systems and methods) and US patent publication No. 2008/0247341 A1 (titled “Digital video interface with bi-directional half-duplex clock channel used as auxiliary data channel).
In US patent publication No. 2008/0152024 A1, the data transmission direction is controlled by the transmission and reception switch signal from communication controller. The transmission and reception circuit periodically switches the transmission direction and reception direction according to an indication by the communication controller depending on the control signal. The structure needs a higher-order LSI (Large Scale Integrated circuit) to be a master and other to be a target to determine the data flow and timing. The data with a different protocol can not communicate with it before data are converted to its format.
In US patent publication No. 2008/0201756 A1, the video channel, auxiliary channel, status channel and supply channel are combined together by frequency multiplexing. High pass, band pass and low pass filters are applied to separate and combine all channels. Various modulation schemes can be used in the system, such as PAM, QAM, etc., in order to maximize data throughput over the single media. However, more channels mean more precise RF (Radio Frequency) components and more crosstalk issue. The complex circuit design and high cost will be a big problem.
In US patent publication No. 2008/0247341 A1, the clock channel is used as an auxiliary data channel to transmit data as well as clock signals in a bidirectional, half-duplex manner using time division multiplexing (TDM). To use the structure, the system must have a clock channel and the repetitive V-Blank (Vertical Blank) is required. It is limited to some video communications only.